Mitochondrial transcription factor A regulates mtDNA copy number in mammals
Mitochondrial transcription factor A regulates mtDNA copy number in mammals
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DOI：
10.1093/hmg/ddh109
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发表时间：
2004-05-01
影响因子：
3.5
通讯作者：
Larsson, NG
中科院分区：
文献类型：
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作者：
Ekstrand, MI;Falkenberg, M;Larsson, NG
线粒体DNA（mtDNA）拷贝数调控在多种人类mtDNA突变疾病中改变，并且在多种正常生理过程中也是重要的。线粒体转录因子A（TFAM）是人类mtDNA转录所必需的，我们在这里证明它也是mtDNA拷贝数的关键调节因子。我们最初进行了体外转录研究，并确定，人TFAM蛋白是一个穷人的激活小鼠mtDNA转录，尽管其非特异性DNA结合能力高。接下来，我们产生了普遍表达人TFAM的P1人工染色体（PAC）转基因小鼠。引入的人TFAM基因以与内源性小鼠Tfam基因类似的方式调节，并且人TFAM蛋白在小鼠中的表达不会导致内源性表达的下调。因此，PAC-TFAM小鼠TFAM蛋白净过表达，这导致mtDNA拷贝数的普遍增加。我们使用了TFAM过表达和TFAM敲除小鼠的组合，并证明了mtDNA拷贝数与小鼠胚胎中的总TFAM蛋白水平成正比。有趣的是，小鼠中人TFAM的表达导致mtDNA拷贝数的上调，而不增加呼吸链容量或线粒体质量。因此，有可能通过实验将mtDNA拷贝数调控与哺乳动物体内mtDNA表达和线粒体生物合成分离开来。总之，我们的研究结果提供了一个新的作用TFAM直接调节哺乳动物mtDNA拷贝数的遗传证据。
Mitochondrial DNA (mtDNA) copy number regulation is altered in several human mtDNA-mutation diseases and it is also important in a variety of normal physiological processes. Mitochondrial transcription factor A (TFAM) is essential for human mtDNA transcription and we demonstrate here that it is also a key regulator of mtDNA copy number. We initially performed in vitro transcription studies and determined that the human TFAM protein is a poor activator of mouse mtDNA transcription, despite its high capacity for unspecific DNA binding. Next, we generated P1 artificial chromosome (PAC) transgenic mice ubiquitously expressing human TFAM. The introduced human TFAM gene was regulated in a similar fashion as the endogenous mouse Tfam gene and expression of the human TFAM protein in the mouse did not result in down-regulation of the endogenous expression. The PAC-TFAM mice thus had a net overexpression of TFAM protein and this resulted in a general increase of mtDNA copy number. We used a combination of mice with TFAM overexpression and TFAM knockout and demonstrated that mtDNA copy number is directly proportional to the total TFAM protein levels also in mouse embryos. Interestingly, the expression of human TFAM in the mouse results in up-regulation of mtDNA copy number without increasing respiratory chain capacity or mitochondrial mass. It is thus possible to experimentally dissociate mtDNA copy number regulation from mtDNA expression and mitochondrial biogenesis in mammals in vivo. In conclusion, our results provide genetic evidence for a novel role for TFAM in direct regulation of mtDNA copy number in mammals.